i have no clue. but i can confirm this issue. i have installed media-sound/pulseaudio-2.1-r1 with USE="X alsa asyncns caps dbus gdbm glib gtk ipv6 orc ssl tcpd udev webrtc-aec". besides, sound is working great for my single-user system.

We all know that pulseaudio is "linux audio done right" (like systemd is "linux init done right" or dbus is "linux IPC done right").
And in the past pulseaudio devs often stated that problems with pulseaudio are due to bad integration by distributions. So removing the pulseaudio bug tracker was the only logical step.